Producing better biofuels

Advanced technology and improved farming methods have helped to boost sugar-cane productivity over the last decades. Raízen, the joint venture between Shell and Cosan, uses ways to make the sugar-cane-to-ethanol process more efficient.

From cultivation to use sugar-cane ethanol produces around 70% less carbon dioxide (CO2) than conventional petrol, taking into account factors such as transport and processing. As it grows, sugar cane generally absorbs CO2 at a greater rate than other biofuel crops such as soy.

Raízen is one of Brazil’s largest producers of ethanol. The approach it takes also reduces CO2 emissions in other ways. For instance, like other ethanol producers Raízen turns by-products into natural fertilisers for sugar cane: nutrient-rich crumbly solids, left from filtering the juice after the sugar cane is crushed in the mills, and a liquid known as vinasse, left when the ethanol is distilled. Raízen also burns leftover plant fibres, known as bagasse, to power its mills. Excess power is supplied to the national grid.

Electricity from bagasse in the ethanol industry was already meeting 3% of Brazil’s demand in early 2012 and this is expected to rise to 18% by 2020. At some of Raízen’s mills sugar-cane juice is extracted by a process that relies on hot water to extract the juice, rather than squeezing it out with rollers. Chopped cane moves on a covered conveyor belt as hot water is pumped in. The water naturally draws the juice out of the cane. More juice is extracted than in the conventional process and the bagasse is drier, making it easier to burn for electricity.

Fuel from waste

Over the coming years some plant waste from the sugar-cane ethanol process could potentially go into making advanced biofuels. In one process enzymes break down the cellulose in plant fibres to produce ethanol. Raízen has the potential to help accelerate the commercial production of biofuels from crop waste and inedible plants.

Raízen has interests in Codexis and Iogen, both technology firms. Iogen uses enzymes to break down the cellulose in plant walls and turn it into sugars. These are then fermented and distilled into ethanol. Codexis develops natural enzymes into “super-enzymes” for the faster conversion of biomass to ethanol, as well as directly into components similar to petrol and diesel. “Instead of burning the plant waste, enzymes could break it down,” says Professor Edgar Ferreira de Beauclair from São Paulo State University. “The cost of doing this on an industrial scale is still a challenge: it will take time to achieve.”

Raising crop yields

Sugar-cane production has become increasingly efficient over the last decades. The Center for Technology in Sugar Cane has cultivated sugar-cane varieties with higher yields and more resistance to pests and disease. Raízen releases Cortesia wasps and cultivates mould that attack the larvae of the two main sugar-cane pests, the spittle bug and sugar-cane borer moth. This approach cuts the use of chemical pesticide by up to 35%.

Raízen uses its own advanced geographical information system that uses satellite imaging to map its 800,000 acres of land. The system draws on a number of sources, such as official soil records, public weather stations and real-time imaging. Advanced mathematical modelling calculates how conditions affect crops and make accurate predictions on sugar-cane yields. It also helps to better inform agricultural managers.

“We use the information on the condition of the crops to adjust, for example, the application of fertiliser or to target pest control for better productivity,” says Ralph Hammer, a Raízen agricultural engineer. “Satellite imaging shows us the fields where anomalies are present, caused by factors such as pests. This is more accurate than sending people out to do spot checks.”

Efficient cutting

Manual workers use machetes to harvest sugar cane. But new requirements due to take effect in 2014 in the main sugar-cane growing state São Paulo call for mechanical harvesters to be used on all land flat enough for such machines to operate (an incline of less than 12%).

At the end of 2014, 97% of Raízen’s harvesting was mechanised.

Mechanical harvesters are more efficient than manual cutting. In addition, if cane is cut manually, hard straw around the cane must be burned first.

Mechanisation removes the need for burning straw because the harvesters can cut through it.

It is estimated that the transition to mechanisation will save 8.5 million tonnes of CO2 emissions industry-wide between now and 2017.